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Light Sensing LED Flashlight

Introduction: Light Sensing LED Flashlight

Every day, lots and lots of electricity and energy is wasted from people accidentally leaving electronics on, or flashlights. This invention is the perfect solution to that problem. The flashlight only turns on when it senses that the room is dark enough to need a light. It reduces energy and electricity waste, and makes sure you never leave your flashlight on. This is also a very simple circuit, so it is good for beginners, and can be modified to suit your needs.

Step 1: Materials

For this project you will need:

A breadboard

CR2032 Battery Holder

CR2032 batteries

Small PCB (optional)

Infrared photo transistor

White LED

NPN transistor

Resistor

Step 2: Wire the Breadboard Circuit

Wire the breadboard circuit according to the pictures.

Step 3: Soldering the Circuit

First, solder both resistor's ends to the right pin and middle pin of the transistor. Then, solder the photo transistor's leads to the left and middle pins. Finally, solder the LED's leads to the transistor's left and middle leads.

Step 4: Adding the Battery Holder

Now, add the battery holder to the circuit. The side with the photo transistor on it is the positive side.

Step 5: Electrical Taping

Finally, all you have to do is wrap electrical tape around the flashlight to keep everything in place, and you are done!

Step 6: The Finished Product

Congratulations! You have made your own light sensing flashlight! From here, there are many things you can do with this very simple circuit.

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11 Comments

Interesting. I found this same circuit in a rechargeable solar light I bought in a dollar store a while back, and I ripped it out and installed it on a paintball mask as a hands-free flashlight! I never could find out what the unmarked transistor was, though. Thanks!